The present invention relates to a drum for fabrication of tires and a process for using such a drum to assemble a tire. The state of the art knows of a considerable number of different types of such drums, from the most simple to the most complex. Some of these have been specially developed for only one part of the building of a green tire: one therefore speaks of first stage drums or second stage drums. Other drums are designed to handle a green tire during the entire period of its building (drum for building in one phase).
The present invention is aimed particularly at drums with shoulders, that is, drums designed to build the beads of the tires on the lateral edges of the drum, and not on the radially upper surface of the drum.
Among these drums, one knows namely holders comprising several parts assembled upon each other, on which a green tire is built, and which are then demounted from the interior of the tire after building. However, such holders can only be used for a single size of tire, and moreover their assembly and especially their disassembly can prove to be complex, even difficult in applications where this disassembly is done manually.
U.S. Pat. No. 3,778,326 gives an example of a more automated drum. This drum can take a spread-out position in which it defines a holder for manufacturing of a tire carcass and a retracted position allowing removal of the carcass after manufacturing. Even if this patent indicates that it is possible to adjust the drum for different widths of tires to be produced, in practice, these possibilities of adjustment are extremely limited. Also, the shoulder of the drum provides a sufficiently continuous and rigid support only for one value of axial distance. In fact, the radial upper bend of the rods can be aligned with the end of the crosspieces only for one and only one relative distance for the sleeves holding the rods. Here again, such a drum must be considered as lending itself only to the manufacturing of a single tire size.
Patent FR 1 492 577 describes a drum whose design is particularly associated with realizing a rigid support with good continuity on the shoulder. However, the walls of such a drum, because they are only comprised of one pneumatic surface, do not provide a sufficiently precise reference for confection of a tire.